Low-resilience limited flight golf ball

ABSTRACT

A limited distance golf ball includes a core and at least one cover layer. The core includes a blend of high-cis polybutadiene and either acrylonitrile-1,3-butadiene or isobutylene-isoprene copolymer or a combination thereof. The limited distance golf ball has a coefficient of restitution (C.O.R.) of less than 0.710 at a test velocity of 125 ft/s, and/or less than 0.660 at a test velocity of 175 ft/s.

FIELD OF THE INVENTION

The present invention relates generally to a limited flight golf ball, wherein the limited flight is obtained through a reduction in resilience properties of the core.

BACKGROUND OF THE INVENTION

Golf balls for use on practice ranges, referred to as “range balls,” have been sold for a number of years. Generally, golf balls sold as range balls are similar in performance to standard golf balls, although range balls are generally designed for increased impact durability and wear durability. However, the distance performance of conventional range balls is similar to that of a standard golf ball.

Practice ranges that have limited space require a “limited flight” range ball. Range balls suitable for use as “limited flight” range balls have been sold for a number of years. Examples of “limited flight” range balls are the Wilson® CF Range, manufactured by Wilson Sporting Goods, and the Spalding® Limited Flight Range ball, manufactured by the Callaway Golf Company. These balls are similar in construction to conventional range balls. The flight distance is restricted (reduced) through the use of an inefficient dimple pattern, which results in shorter distance than conventional range balls. However, these less efficient dimple patterns produce shorter flight distance through undesirable and objectionable flight trajectory. Specifically, the short distance is obtained through a pattern with shallow dimples, resulting in a very high trajectory, described as “ballooning.” This trajectory is objectionable to the golfer, and is not beneficial to the golfer “practicing” his swing.

There are also one-piece range golf balls available, such as the Srixon® range ball, available from SRI Sports Limited Corporation. These balls generally are short in flight distance, but have playability properties (such as feel) that are significantly different than a conventional golf ball. These golf balls are also not ideal for practice purposes.

Thus, there is a continuing need for a limited flight range golf ball that achieves a shorter flight distance than a standard golf ball without the undesirable trajectory, or “ballooning,” or playability properties that differ significantly from conventional golf balls, as observed on currently produced limited flight balls.

SUMMARY OF THE INVENTION

The invention provides a limited distance golf ball including a core and at least one cover layer. The core has a coefficient of restitution (“C.O.R.”) of less than 0.710 at a test velocity of 125 ft/s, or less than 0.660 at a test velocity of 125 ft/s, or less than 0.660 at a test velocity of 175 ft/s. The relatively low resilience properties of the core produce a limited flight distance without significantly affecting the flight trajectory performance of the golf ball.

According to a principal aspect of the invention, the core of the multi-piece limited distance golf ball includes a blend of high-cis polybutadiene and either acrylonitrile-1,3-butadiene or isobutylene-isoprene copolymer or a combination thereof. The high-cis polybutadiene suitably has a cis-1,4 content of greater than 94%.

In one embodiment of the invention, the core of the multi-piece limited distance golf ball includes 20-80 parts (by weight) per hundred parts (by weight) of rubber (“phr”) of the high-cis polybutadiene; 80-20 phr by weight of acrylonitrile-1,3-butadiene; 20-40 phr of a co-crosslinking agent; 0-10 phr of an activator; 10-30 phr of an inert filler; and 0.5-3 phr of a free-radical initiator. The acrylonitrile-1,3-butadiene suitably has an acrylonitrile content greater than 25%, such as 30-40%, or 30-36%.

In another embodiment of the invention, the core of the multi-piece limited distance golf ball includes 20-80 phr of the high-cis polybutadiene; 80-20 phr by weight of isobutylene-isoprene copolymer; 2040 phr of a co-crosslinking agent; 0-10 phr of an activator; 10-30 phr of an inert filler; and 0.5-3 phr of a free-radical initiator. The isobutylene-isoprene copolymer suitably has a chlorine content of 1-2%.

The free radical initiator may be a peroxide, such as dicumyl peroxide, tert-butyl peroxybenzoate, butyl 4,4′-di-(tert-butylperoxy) valerate, or 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane.

The cover layer or layers may include such materials as ionomers, polyurethanes, polyesters, polyolefins, ethylene-methacrylic acid copolymers, ethylene-acrylic acid copolymers, or any combination of these materials. The limited distance golf ball suitably has a conventional dimple pattern, which allows for flight trajectory properties similar to a conventional golf ball.

In certain embodiments, the limited distance golf ball has a deflection of between 0.065 and 0.130 inch under a 200 pound (lb.) static load.

This invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings described herein below, and wherein like reference numerals refer to like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a golf ball in accordance with a preferred embodiment of the invention.

FIG. 2 is cross-section view of the golf ball of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to an improved limited flight golf ball, in particular, a limited flight golf ball composed of multiple pieces and having low resilience properties compared to conventional golf balls. Referring to FIGS. 1-2, a preferred embodiment of a multi-layered limited flight golf ball is indicated generally at 10. The ball 10 includes a core 12 and a cover layer 14.

The limited flight golf ball 10 has a conventional dimple pattern, which allows for flight trajectory properties similar to a conventional golf ball. The limited flight is achieved through reduced C.O.R. (coefficient of restitution) properties in the core 12. The limited C.O.R. properties in the core 12 results in a golf ball 10 having a significantly lower initial velocity when struck with a golf club, which in turn results in shorter distance properties. The use of a lower resilience (C.O.R.) core 12 as described herein further results in greater impact durability than a golf ball made using a conventional golf ball core.

The core 12 is a substantially spherical, generally solid member positioned at the geometric center of the ball 10. The core 12 is formed of a blend of high-cis polybutadiene rubber and either acrylonitrile-butadiene rubber (NBR) or isobutylene-isoprene copolymer or a combination thereof to produce the desired C.O.R. properties, namely a C.O.R. of less than 0.710 at a test velocity of 125 ft/s, or less than 0.660 at a test velocity of 125 ft/s, or less than 0.660 at a test velocity of 175 ft/s. More particularly, the core 12 is formulated using a blend of the rubber, a co-crosslinking agent, a free radical initiator, and fillers as necessary to provide acceptable density. Acrylonitrile-butadiene rubber is less expensive than isobutylene-isoprene copolymer. Thus, from a cost-saving standpoint, it may be preferable to use acrylonitrile-butadiene rubber or a combination of acrylonitrile-butadiene rubber and isobutylene-isoprene copolymer rather than isobutylene-isoprene copolymer alone.

The high-cis polybutadiene, more particularly cis-1,4-polybutadiene, suitably has a cis-1,4 content of greater than 94%. Polybutadiene rubber suitable for use in the core 12 can be synthesized using nickel, cobalt, or neodymium catalysts. Examples of suitable polybutadiene materials made using neodymium catalyzed materials include Enichem® BR-40 (produced by Polimieri Europa) and Neodene® BR40 (produced by Karbochem). Examples of polybutadiene materials made using nickel catalyzed materials include Budene® 1207 (produced by the Goodyear Tire and Rubber Company) and Kuhmo™ KBR-01 (produced by Kuhmo Tire and Rubber). In one embodiment, the core composition includes 20-80 phr (parts per hundred parts rubber) of the high-cis polybutadiene. In another embodiment, the core composition includes 40-60 phr of the high-cis polybutadiene.

The acrylonitrile-butadiene rubber, more particularly acrylonitrile-1,3-butadiene, suitably has an acrylonitrile content of greater than 25%. For example, the acrylonitrile content may be between 30 and 40%, or between 30 and 36%. In one embodiment, the core composition includes 80-20 phr by weight of acrylonitrile-butadiene. In another embodiment, the core composition includes 6040 phr by weight of acrylonitrile-butadiene.

The isobutylene-isoprene copolymer is suitably chlorobutyl rubber, which is a chlorinated isobutylene-isoprene copolymer. The chlorinated isobutylene-isoprene copolymer suitably has a chlorine content of greater than 1% by weight of the total polymer. For example, the chlorine content of the chlorinated isobutylene-isoprene copolymer may be between 1 and 2% by weight of the total polymer. In one embodiment, the core composition includes 80-20 phr by weight of isobutylene-isoprene copolymer. In another embodiment, the core composition includes 6040 phr by weight of isobutylene-isoprene copolymer.

The co-crosslinking agent improves the stiffness and resiliency of the core 12. In one embodiment, the core composition includes 20-40 phr of the co-crosslinking agent. In another embodiment, the core composition includes 20-30 phr of the co-crosslinking agent In a particularly preferred embodiment, the co-crosslinking agent is a zinc salt of an unsaturated acrylate ester. Zinc diacrylate is one preferred metal salt. Further, a level of fatty acid salt of up to 10% of the total of the zinc diacrylate and fatty acid salt is appropriate. For example, the zinc salt of an unsaturated acrylate can be approximately 92 percent zinc diacrylate and 8 percent stearate. Materials suitable for use as the co-crosslinking agent are produced by Sartomer, Inc.

A metal oxide activator is optional, and may be included in the core composition in an amount of 0-10 phr. The metal oxide activator may be zinc oxide. In addition to serving as an activator, zinc oxide also enables the composition of the core 12 to cure faster thereby reducing the manufacturing time of the core 12.

The composition of the core also preferably includes 0.5-3 phr of a free-radical initiator. In one preferred embodiment, the free radical initiator is a peroxide. Peroxides such as dicumyl peroxide, tert-butyl peroxybenzoate, butyl 4,4′-di-(tert-butylperoxy) valerate, and 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane are suitable for use. Dicumyl peroxide (sold by Akzo under the trade name Percadox® BC) and 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane (sold by Akzo under the tradename Trigonox® 29/40) are preferred for use in the core compound.

In alternative embodiments, other amounts of one or more of the co-crosslinking agent, the metal oxide activator, and the free radical initiators can be used. Additionally, alternative cross-linking agents, metal oxide activators, and free radical initiators can also be used.

Inert fillers suitable for use in adjusting the density of the core 12 can be chosen from either inorganic or organic materials. Preferred materials for adjusting the density of the core include inorganic materials such as zinc oxide, barium sulfate, titanium dioxide, and mixtures thereof. The total amount of the inert fillers in the core composition may be 10-30 phr, as necessary to provide the desired weight of the golf ball.

The composition of the core 12 is mixed, molded, and then glebarred to a desired diameter. In a preferred embodiment, the core 12 has an outside diameter within the range of 1.48 to 1.58 inches. The core suitably has a deflection of between 0.065 and 0.130 inch under an applied static load of 200 lbs., and a C.O.R. of less than 0.710 at a test velocity of 125 ft/s. In another preferred embodiment, the core has a deflection between 0.080 and 0.125 inch under a 200 lb. static load, and a C.O.R. of less than 0.660 at a test velocity of 125 ft/s. The core 12 can also be formed in other sizes and can have a compression or deflection value outside of 0.065 and 0.130 inch, or 0.080 and 0.125 inch, under an applied load of 200 lbs.

The cover layer 14 is a spherical covering that encompasses the core 12. The cover layer 14 may include one or more layers. The cover layer 14 may be molded about the core 12. For example, urethane balls may be processed using a cast molding process. Materials suitable for use in the cover(s) of this ball include, but are not limited to: ionomers, polyurethanes, polyesters, polyolefins, ethylene-methacrylic acid copolymers, ethylene-acrylic acid copolymers, and mixtures thereof.

The cover layer 14 is formed to a desired thickness and hardness. In a preferred embodiment, the cover layer 14 has a thickness within the range of 0.0300 to 0.100 inches, and a hardness within the range of 45 to 75 on the Shore D hardness scale. In another preferred embodiment, the cover layer 14 has a thickness within the range of 0.060 to 0.080 inches, and a hardness of at least 60 on the Shore D hardness scale. The cover layer 14 can also be formed in other sizes and with a hardness outside of the range of 45 to 75, or below 60, on the Shore D hardness scale.

The limited distance golf ball 10 has a conventional dimple pattern, which allows for flight trajectory properties similar to a conventional golf ball. For example, the dimples may cover more than 75% of an outer surface of the ball.

The resulting golf ball 10 made according to the invention produces a limited flight distance through a reduction in the resilience properties (C.O.R.) of the core. However, the reduction in resilience properties of the core 12 does not significantly affect the flight trajectory performance of the golf ball 10. The limited flight golf ball 10 in accordance with the invention results in a shorter golf ball without the undesirable trajectory, or “ballooning,” that is observed on currently produced multi-piece limited flight balls.

The ball 10 also fully conforms to the United States Golf Association® (“USGA®”) requirements for golf balls specified in the USGA®, “The Rules of Golf And The Rules Of Amateur Status 2002-2003”, effective Jan. 1, 2002, which is incorporated by reference. Appendix III of the USGA® Rules of Golf includes the following ball requirements:

1. Weight

-   -   The weight of the ball shall not to be greater than 1.620 ounces         avoirdupois (45.93 gm).

2. Size

-   -   The diameter of the ball shall not be less than 1.680 inches         (42.67 mm). This specification will be satisfied if, under its         own weight, a ball falls through a 1.680 inches diameter ring         gauge in fewer than 25 out of 100 randomly selected positions,         the test being carried out at a temperature of 23+/−1 degree C.

3. Spherical Symmetry

-   -   The ball must not be designed, manufactured or intentionally         modified to have properties which differ from those of a         spherically symmetrical ball.

4. Initial Velocity

-   -   The initial velocity of the ball shall not exceed the limit         specified (test on file) [250 ft/s+2%, or 255 ft/s] when         measured on apparatus approved by the United States Golf         Association.

5. Overall Distance Standard

-   -   The combined carry and roll of the ball, when tested on         apparatus approved by the United States Golf Association, shall         not exceed the distance specified under the conditions set forth         in the Overall Distance Standard for golf balls on file with the         United States Golf Association.

The present invention is further illustrated by the following examples. The present invention is not limited to the following examples, and various changes and modifications may be made in the invention without departing from the spirit and scope thereof.

EXAMPLE 1

Golf ball cores having low resilience properties suitable for use in limited flight golf balls were designed and produced in accordance with the invention. The Example 1 balls were made with the following formulas. TABLE 1 Core Formulas/Properties C-1 C-2 C-3 C-4 Cont Material (phr) Budene ® 1207 50 50 75 50 100 Polybutadiene Europrene ® N-3330 50 50 — — — Acrylonitrile Lanxess ® — — 25 50 — Chlorobutyl 1255 Sartomer ® SR416D 27 29 22 24 27 Zinc Oxide 5 5 5 5 5 Zinc Stearate 3 3 3 3 3 Barytes 10 8 17.5 18 17.5 Percadox® BC 0.99 0.99 0.99 0.99 0.99 Core Physical Properties Diameter (inches) 1.551 1.549 1.544 1.549 1.544 Weight (grams) 36.88 37.03 36.86 36.95 37.18 Deflection* 0.120″ 0.109″ 0.114″ 0.120″ 0.107″ (200 lb. Load) Compression** 64.0 72.8 68.8 64.0 74.8 C.O.R. (125 ft/s)*** 0.597 0.605 0.691 0.591 0.793 *Deflection measurements were taken under a 200 lb. applied load, using a Wilson Dead Weight Deflection testing machine. **Compression for golf ball cores is calculated using the following formula: Comp. = 160 − 0.8(1000 × Deflection) ***“C.O.R. (125 ft/s)” refers to the ratio of outbound/inbound velocity with a 125 ft/s inbound velocity test setup.

Budene® 1207 is a nickel catalyzed high-cis content polybutadiene rubber produced by The Goodyear Tire and Rubber Company.

Europrene® N-3330 is an acrylonitrile-1,3-butadiene copolymer produced by Polimieri Europa. This material has an ACN content of 32 to 34%.

Lanxess® Chlorobutyl 1255 is a chlorinated isobutylene-isoprene copolymer having chlorine content of 1.25%. This material is produced by Lanxess, Inc.

Sartomer® SR416D includes ˜92% by weight of zinc diacrylate and ˜8% by weight of zinc stearate. This material is supplied by the Sartomer Company, Inc.

Percadox® BC is a dicumyl peroxide having an activity level of ˜99%. This material is produced by Akzo Nobel Chemicals, Inc.

Descriptions of the properties of the molded cores of samples C-1 through C-4 as compared to a conventional golf ball core (Cont.) are as follows:

Sample C-1: Core Sample C-1 was formulated of a blend of 50 phr Budene® 1207 high cis-polybutadiene and 50 phr of Europrene® N-3330 acrylonitrile-1,3-polybutadiene. The core was mixed and molded using conventional techniques for golf ball cores. The resultant core had a deflection, compression, weight, etc., comparable to the control core. The C.O.R. of Sample C-1 was 0.597, which is significantly lower than the control core, which yielded a C.O.R. value of 0.793.

Sample C-2: Core Sample C-2 was also formulated of a blend of 50 phr Budene® 1207 high cis-polybutadiene and 50 phr of Europrene® N-3330 acrylonitrile-1,3-polybutadiene. This core had a higher level of co-crosslinking agent than sample C-1. The core was mixed and molded using conventional techniques for golf ball cores. The resultant core had a deflection, compression, weight, etc., comparable to the control core. The C.O.R. of Sample C-2 was 0.605, which is significantly lower than the control core, which yielded a C.O.R. value of 0.793.

Sample C-3: Core Sample C-3 was formulated of a blend of 75 phr of Budene® 1207 high cis-polybutadiene and 25 phr of Lanxess® 1255 chlorobutyl rubber. The core was mixed and molded using conventional techniques for golf ball cores. The resultant core had a deflection, compression, weight, etc., comparable to the control core. The C.O.R. of Sample C-3 was 0.691, which is significantly lower than the control core, which yielded a C.O.R. value of 0.793.

Sample C-4: Core Sample C-4 was formulated of a blend of 50 phr of Budene® 1207 high cis-polybutadiene and 50 phr of Lanxess® 1255 chlorobutyl rubber. The core was mixed and molded using conventional techniques for golf ball cores. The resultant core had a deflection, compression, weight, etc., comparable to the control core. The C.O.R. of Sample C-4 was 0.591, which is significantly lower than the control core, which yielded a C.O.R. value of 0.793.

Golf ball cores as described in Table 1 were molded into balls. Two different cover formulas (CV-1 and CV-2) were used in evaluating the effect of the lower resilience cores on the flight properties of the golf ball. The cover formulas (CV-1 and CV-2) applied to the cores in Table 1 and the cover formula of a conventional golf ball (Cont.) are described in Table 2. TABLE 2 Golf Ball Cover Formulations Cover ID Formula CV-1 Surlyn ® 8528/Surlyn ® 9520 @ 50/50 CV-2 Surlyn ® 8140/Surlyn ® 9320 @ 50/50 Cont. Surlyn ® 8940/Surlyn ® 9910 @ 50/50

Surlyn® 8528 is a copolymer including ˜90% by weight ethylene and ˜10% by weight methacrylic acid. Approximately 54% of the methacrylic acid groups are neutralized with sodium ions.

Surlyn® 9520 is a copolymer including ˜90% by weight ethylene and ˜10% by weight methacrylic acid. Approximately 71% of the methacrylic acid groups are neutralized with zinc ions.

Surlyn® 8140 is a copolymer including ˜81% by weight ethylene and ˜19% by weight methacrylic acid. Approximately 50% of the methacrylic acid groups are neutralized with sodium ions.

Surlyn® 9320 is a terpolymer including ˜67-70% by weight ethylene, ˜10% by weight methacrylic acid, and ˜20-23% by weight n-butyl acrylate. Approximately 70% of the methacrylic acid groups are neutralized with zinc ions.

Surlyn® 8940 is a copolymer including ˜85% by weight ethylene and ˜15% by weight methacrylic acid. Approximately 29% of the methacrylic acid groups are neutralized with sodium ions.

Surlyn® 9910 is a copolymer including ˜85% by weight ethylene and ˜15% by weight methacrylic acid. Approximately 58% of the methacrylic acid groups are neutralized with zinc ions.

All of the ionomers described above are produced by E.I. duPont de Nemours and Company.

Golf balls were molded with cores C-1 and C4 as described in Table 1 and covers CV-1 and CV-2 as described in Table 2. Ball properties were as follows: TABLE 3 Golf Ball Properties EX-1 EX-2 EX-3 EX-4 CB-1 Core C-1 C-1 C-4 C-4 Cont Cover CV-1 CV-2 CV-1 CV-2 CV-2 Golf Ball Physical Properties Size 1.681″ 1.683″ 1.681″ 1.684″ 1.683″ Weight 45.23 45.52 45.21 45.54 45.72 Deflection 0.105″ 0.108″ 0.105″ 0.106″ 0.100″ Compression* 75.0 72.0 75.0 74.0 80.0 C.O.R. (150 ft/s)** 0.597 0.603 0.591 0.594 0.764 C.O.R. (175 ft/s)** 0.592 0.594 0.582 0.588 0.744 Initial Velocity*** 232.4 231.6 231.6 231.5 256.7 Impact Dur. (175 ft/s)+ 182.7 248.0 127.5 218.7 78.8 *Compression for golf balls is calculated using the following formula: Comp. = 180 − (1000 × Deflection) **“C.O.R. (150 ft/s)” refers to the ratio of outbound/inbound velocity with a 150 ft/s inbound velocity test setup. “C.O.R. (175 ft/s)” refers to the ratio of outbound/inbound velocity with a 175 ft/s inbound velocity test setup. ***“Initial Velocity” was measured using the Wilson Initial Velocity Test Machine. +Impact durability was tested by shooting balls into a steel plate at a test velocity of 175 ft/s. The number of hits until failure is noted.

Descriptions of the properties of the molded cores of samples C-1 and C-4 in combination with covers CV-1 and CV-2 as compared to a conventional golf ball core (Cont.) with cover CV-2 are as follows:

Example EX-1: The golf ball of Example EX-1 was molded using core C-1 (including a polybutadiene/acrylonitrile rubber blend) and cover CV-1 (10% acid ionomers). The resultant ball had compression comparable to the control ball CB-1. A decrease of ˜0.150 in C.O.R. was observed compared to reference ball CB-1. Further, a decrease in initial velocity of ˜24 ft/s compared to reference ball CB-1 was observed. This will result in significant loss in flight distance. Further, the impact durability of EX-1 example ball was approximately 132% higher than that of control ball CB-1. This is particularly beneficial for a potential range ball application.

Example EX-2: The golf ball of Example EX-2 was molded using core C-1 (including a polybutadiene/acrylonitrile rubber blend) and cover CV-2 (High acid/V.L.M.I. ionomer blend). The resultant ball had compression comparable to the control ball CB-1. A decrease of ˜0.150 in C.O.R. was observed compared to reference ball CB-1. Further, a decrease in initial velocity of ˜25 ft/s compared to reference ball CB-1 was observed. This will result in significant loss in flight distance. Further, the impact durability of EX-2 example ball was approximately 215% higher than that of control ball CB-1. This is particularly beneficial for a potential range ball application.

Example EX-3: The golf ball of Example EX-3 was molded using core C-4 (including a polybutadiene/chlorobutyl rubber blend) and cover CV-1 (10% acid ionomers). The resultant ball had compression comparable to the control ball CB-1. A decrease of ˜0.160 in C.O.R. was observed compared to reference ball CB-1. Further, a decrease in initial velocity of ˜25 ft/s compared to reference ball CB-1 was observed. This will result in significant loss in flight distance. Further, the impact durability of EX-3 example ball was approximately 62% higher than that of control ball CB-1. This is particularly beneficial for a potential range ball application.

Example EX-4: The golf ball of Example EX4 was molded using core C-4 (including a polybutadiene/chlorobutyl rubber blend) and cover CV-2 (High acid/V.L.M.I. ionomer blend). The resultant ball had compression comparable to the control ball CB-1. A decrease of ˜0.160 in C.O.R. was observed compared to reference ball CB-1. Further, a decrease in initial velocity of ˜25 ft/s compared to reference ball CB-1 was observed. This will result in significant loss in flight distance. Further, the impact durability of EX-4 example ball was approximately 178% higher than that of control ball CB-1. This is particularly beneficial for a potential range ball application.

EXAMPLE 2

Based upon results of the trials in Example 1 above, further examples of limited flight distance balls were molded to determine the level of distance loss that results from using cores described in accordance with the invention. A standard range ball construction (Cont-2) was used for reference purposes. TABLE 4 Core Formulas/Properties C-5 C-6 Cont-2 Material (phr) Kuhmo ™ KBR-01 Polybutadiene 50 50 100 Europrene ® N-3330 Acrylonitrile 50 50 — Sartomer ® SR416D 27 29 27 Barytes 19 19 26 Trigonox ® 29A 1.33 1.33 1.33 Core Physical Properties Diameter (inches) 1.5110″ 1.5077″ 1.5121″ Weight (grams) 34.94 34.94 35.19 Deflection (200 lb. load) 0.1131″ 0.0957″ 0.0975″ Compression 69.5 83.4 82.0 C.O.R. (125 ft/s) 0.632 0.644 0.781

Kuhmo™ KBR-01 is a nickel catalyzed high-cis content polybutadiene rubber produced by the Kuhmo Tire and Rubber Company.

Trigonox® 29A is a 1,1-Di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane peroxide having an activity level of ˜100%. This material is produced by Akzo Nobel Chemicals, Inc.

Descriptions of the properties of the molded cores of samples C-5 and C-6 as compared to a conventional range ball core (Cont-2) are as follows:

Sample C-5: The golf ball core of Sample C-5 yields a lower compression (˜13 pt.) than Cont-2 range core. A decrease in C.O.R. of ˜0.150 is observed.

Sample C-6: The golf ball core of Sample C-6 yields a comparable compression compared to Cont-2 range core. A decrease in C.O.R. of ˜0.140 is observed.

The cores illustrated in Table 4 were molded into balls using the following cover formulation: Iotek® 8020/Iotek® 7010/Nucrel® 925N at a ratio of 41/56/3.

Iotek® 8020 is a copolymer comprising ˜85% by weight of ethylene and ˜15% by weight of acrylic acid. Approximately 27% of the acrylic acid groups are neutralized with sodium ions. Iotek® 7010 is a copolymer comprising ˜85% by weight of ethylene and ˜15% by weight of acrylic acid. Approximately 35% of the acrylic acid groups are neutralized with zinc ions. Nucrel® 925 is a copolymer comprising ˜85% by weight of ethylene and ˜15% by weight of methacrylic acid. Iotek® ionomers are produced by ExxonMobil Chemical Company. Nucrel® is produced by E.I. duPont de Nemours and Company. TABLE 5 Core Formulas/Properties EX-5 EX-6 CB-2 Material Core C-5 C-6 Cont-2 Ball Physical Properties Diameter (inches) 1.6834 1.6832 1.6828 Weight (grams) 45.39 45.51 45.67 Deflection (200 lb. load) 0.0823″ 0.0737″ 0.0729″ Compression 97.7 106.3 107.1 C.O.R. (175 ft/s) 0.637 0.644 0.752 Impact Durability (175 ft/s) 120.1 183.1 62.0 Ball Flight Properties (Driver) ^(#) Carry Distance (yd.) 236.8 239.2 262.0 Total Distance (yd.) 246.2 245.7 268.4 Initial Velocity 220.0 222.1 236.8 Apogee 9.8 9.8 10.0 Spin Rate 3123 3264 2847 ^(#) Driver testing performed using True Temper test machine. Testing performed using a clubhead velocity of 160 ft/s and a launch angle of 10°.

Descriptions of the properties of the molded cores of samples C-5 and C-6 in combination with the above-described cover formulation as compared to a conventional range ball (Cont-2) with the same cover formulation are as follows:

Example EX-5: The golf ball of Example EX-5 included a core molded with a blend of high-cis polybutadiene and acrylonitrile-1,3-butadiene. The resulting ball yielded a lower compression than the control range ball CB-2. The ball of Example EX-5 yielded a decrease in C.O.R. of 0.115 compared to the control range ball CB-2. The golf ball of Example EX-5 yielded an increase in impact durability of 93.7% compared to the control range ball CB-2. The golf ball of Example EX-5 yielded a decrease in carry distance of ˜26.5 yd. (9.6%) compared to the control range ball CB-2. The golf ball of Example EX-5 yielded a decrease in initial velocity off the driver club of ˜16 ft/s compared to the control range ball CB-2. The spin rate and apogee of the golf ball of Example EX-5 is comparable to the control range ball CB-2, indicating comparable flight trajectory characteristics.

Example EX-6: The golf ball of Example EX-6 also included a core molded with a blend of high-cis polybutadiene and acrylonitrile-1,3-butadiene. The resulting ball yielded a compression comparable to the control range ball CB-2. The ball of Example EX-6 yielded a decrease in C.O.R. of 0.108 compared to the control range ball CB-2. The golf ball of Example EX-6 yielded an increase in impact durability of 195% compared to the control range ball CB-2. The golf ball of Example EX-6 yielded a decrease in carry distance of ˜23 yd. (8.7%) compared to the control range ball CB-2. The golf ball of Example EX-6 yielded a decrease in initial velocity off the driver club of ˜14 ft/s compared to the control range ball CB-2. The spin rate and apogee of the golf ball of Example EX-6 is comparable to the control range ball CB-2, indicating comparable flight trajectory characteristics.

Examples 1 and 2 illustrate the lower resilience properties of cores that include a blend of high-cis polybutadiene and either acrylonitrile-1,3-butadiene or an isobutylene-isoprene copolymer. These examples further illustrate that the golf balls with the lower-resilient cores have comparable deflection, compression, and weight properties compared to conventional golf balls, while having greater impact durability than conventional golf balls. These examples also illustrate that the golf balls with the lower-resilient cores were carried a shorter distance than a standard range ball, but with comparable flight trajectory characteristics.

While the preferred embodiments of the present invention have been described and illustrated, numerous departures therefrom can be contemplated by persons skilled in the art. Therefore, the present invention is not limited to the foregoing description but only by the scope and spirit of the appended claims. 

1. A limited distance golf ball comprising a core and at least one cover layer, wherein the core includes a blend of: 20-80 phr of the high-cis polybutadiene; 80-20 phr by weight of acrylonitrile-1,3-butadiene; 20-40 phr of a co-crosslinking agent; 0-10 phr of an activator; 10-30 phr of an inert filler; and 0.5 to 3 phr of a free-radical initiator.
 2. The golf ball of claim 1, wherein the high-cis polybutadiene has a cis-1,4 content greater than 94%.
 3. The golf ball of claim 1, wherein the acrylonitrile-1,3-butadiene has an acrylonitrile content greater than 25%.
 4. The golf ball of claim 1, wherein the acrylonitrile-1,3-butadiene has an acrylonitrile content of 30-40%.
 5. The golf ball of claim 1, wherein the acrylonitrile-1,3-butadiene has an acrylonitrile content of 30-36%.
 6. The golf ball of claim 1, wherein the free-radical initiator comprises a peroxide.
 7. The golf ball of claim 6, wherein the peroxide is selected from the group consisting of dicumyl peroxide, tert-butyl peroxybenzoate, butyl 4,4′-di-(tert-butylperoxy) valerate, and 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane.
 8. The golf ball of claim 1, wherein the at least one cover layer comprises a material selected from the group consisting of: ionomers, polyurethanes, polyesters, polyolefins, ethylene-methacrylic acid copolymers, ethylene-acrylic acid copolymers, and mixtures thereof.
 9. The golf ball of claim 1, wherein the at least one cover layer includes a conventional dimple pattern.
 10. The golf ball of claim 1, wherein the golf ball core has a C.O.R. of less than 0.710 at a test velocity of 125 ft/s.
 11. The golf ball of claim 1, wherein the golf ball core has a C.O.R. of less than 0.660 at a test velocity of 125 ft/s.
 12. The golf ball of claim 1, wherein the golf ball has a deflection of between 0.065 and 0.130 inch under a 200 lb. static load.
 13. A limited distance golf ball comprising: a core and at least one cover layer, wherein the core includes a blend of high-cis polybutadiene and acrylonitrile-1,3-butadiene, and the core has a C.O.R. of less than 0.710 at a test velocity of 125 ft/s.
 14. The golf ball of claim 13, wherein the high-cis polybutadiene has a cis-1,4 content greater than 94%.
 15. The golf ball of claim 13, wherein the acrylonitrile-1,3-butadiene has an acrylonitrile content greater than 25%.
 16. The golf ball of claim 13, wherein the acrylonitrile-1,3-butadiene has an acrylonitrile content of 30-40%.
 17. The golf ball of claim 13, wherein the acrylonitrile-1,3-butadiene has an acrylonitrile content of 30-36%.
 18. The golf ball of claim 13, wherein the core further comprises an isobutylene-isoprene copolymer blended with the high-cis polybutadiene and the acrylonitrile-1,3-butadiene.
 19. The golf ball of claim 13, wherein the core further comprises a peroxide.
 20. The golf ball of claim 19, wherein the peroxide is selected from the group consisting of dicumyl peroxide, tert-butyl peroxybenzoate, butyl 4,4′-di-(tert-butylperoxy) valerate, and 1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane.
 21. The golf ball of claim 13, wherein the at least one cover layer comprises a material selected from the group consisting of: ionomers, polyurethanes, polyesters, polyolefins, ethylene-methacrylic acid copolymers, ethylene-acrylic acid copolymers, and mixtures thereof.
 22. The golf ball of claim 13, wherein the at least one cover layer includes a conventional dimple pattern.
 23. The golf ball of claim 13, wherein the core of the limited distance golf ball has a C.O.R. of less than 0.660 at a test velocity of 125 ft/s.
 24. A limited distance golf ball comprising a core and at least one cover layer, wherein the core includes a blend of: 20-80 phr of the high-cis polybutadiene; 80-20 phr by weight of an isobutylene-isoprene copolymer; 20-40 phr of a co-crosslinking agent; 0-10 phr of an activator; 10-30 phr of an inert filler; and 0.5 to 3 phr of a free-radical initiator.
 25. The golf ball of claim 24, wherein the isobutylene-isoprene copolymer has a chlorine content of 1-2%.
 26. The golf ball of claim 24, wherein the at least one cover layer includes a conventional dimple pattern.
 27. The golf ball of claim 24, wherein the golf ball core has a C.O.R. of less than 0.710 at a test velocity of 125 ft/s.
 28. The golf ball of claim 24, wherein the golf ball core has a C.O.R. of less than 0.660 at a test velocity of 125 ft/s. 